This invention relates to an induction system for an engine and more particularly to an improved induction system that improves the performance of the engine at low and midrange conditions without deteriorating high-speed performance.
As is well known, the induction system of an internal combustion engine is extremely important in determining the performance of the engine. Also, with conventional induction systems, the induction system is designed so as to provide a compromise between the requirements of high-speed and low-speed performance. That is, to achieve maximum high-speed performance, the induction system should be designed so as to permit maximum charging of the cylinder. This can be achieved by providing relatively large unrestricted flow passages in which the intake charge enters the cylinder in a direction so as to flow generally parallel to the axis of the cylinder bore.
Although the described type of induction system provides high power outputs, the unobstructed flow and large flow areas tend to reduce the flow velocity entering the cylinder when the engine is operated at low and mid-range speeds. Under these conditions, it is desirable to have the flow velocity entering the chamber to be more rapid and also to introduce some turbulence so as to improve the flame propagation and combustion. However, these turbulence increasing devices can significantly reduce the breathing ability of the engine and its high-speed performance.
Therefore, conventional induction systems provide a compromise between these two extremes with an emphasis on the condition which is more frequently encountered.
There have been proposed, however, a number of devices for cooperation with the induction system so that it can accommodate more readily the requirements of the engine at both high and low speeds as well as providing proper conditions during mid-range performance. For example, in my aforenoted copending application entitled "Tumble Control Valve for Intake Port," Ser. No. 07/834,604, filed Feb. 12, 1992, and assigned to the assignee hereof, there is disclosed an arrangement for a multiple valve engine which includes a control valve that is movable between an unrestricted position so as to provide maximum engine charging and a flow redirecting position wherein different types of flow patterns and different turbulence inducing arrangements may be accomplished in the engine. That system is extremely effective in improving the engine performance.
In the various embodiments shown in that application, there are constructions which are designed so as to provide, in addition to normal, unrestricted charging, either tumble, swirl, or a combination of tumble and swirl. Tumble is a type of swirling motion that occurs in the combustion chamber about an axis that extends transversely to the cylinder bore axis. With this type of motion, the intake charge is introduced from one side of the cylinder bore and flows across no the other side to be redirected in a downward direction where it will strike the head of the piston and then flow back to the side where it is entered so as to accomplish this tumble motion. Swirl, on the other hand, is a rotary motion within the cylinder bore that occurs about the cylinder bore axis. Under some conditions, tumble is preferred and under other conditions, swirl is preferred.
It has been discovered that with some engines and in some running conditions, a still further type of action in the cylinder may be desirable. This is a motion which may be referred to as "slant tumble". With slant tumble, there is superimposed upon the normal tumble action a slight action that tends to cause the charge to flow at an angle to a plane containing the axis of the cylinder bore but one which is not strong enough to be considered swirl. This type of motion is particularly advantageous if the charge to the engine is introduced through the induction system in a somewhat nonhomogeneous fashion because the slant tumble action will promote mixing and improve mixture distribution in the combustion chamber as can be desired.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is a further object of this invention to provide an improved induction system for an internal combustion engine that permits unobstructed charging of the cylinder under high-speed high-load conditions and which will permit the generation of a slant tumble action under other running conditions.
It is a further object of this invention to provide an improved control valve and induction system arrangement that can provide the desired flow patterns under all running conditions.
As has been noted, in order to achieve high power outputs it is desirable to provide an induction system that can fully charge the combustion chamber. This is generally done by providing large, intake valves or, in some instances, multiple intake valves. For example, engines having two intake valves per cylinder are particularly useful in improving charging efficiency under high-speed high-load conditions.
With induction systems that employ plural intake valves and intake valve seats, there may be instances wherein the intake valves are disposed at different distances from a plane containing the axis of the cylinder bore. This situation commonly occurs with engines employing three intake valves per cylinder that comprise a center valve that is farther from the plane containing the cylinder bore axis and a pair of side intake valves that are disposed closer to and may actually intersect this plane. Obviously, the induction systems that supply these valves are disposed so that they have different flow paths because of the different locations of the valve seats which they serve. Thus, in order to control the flow through the induction passages so as to obtain the desired flow pattern, the valve arrangement for controlling the flow through the induction systems can become complicated.
It is, therefore, a further object of this invention to provide an improved induction system and control valve for a multiple valve engine.
It is a further object of this invention to provide an improved induction system for a multiple valve engine embodying a single control valve for controlling the flow through the induction system before it reaches each of the valve ports.
It is a still further object of this invention to provide an improved tumble control valve arrangement for a multiple valve engine wherein a single control valve can control the tumble action through all of the intake ports.